Electrical apparatus generating a low frequency, alternating magnetic field for promoting the growth of bone and other body tissues

ABSTRACT

The growth or repair of fractured bones or the growth of other body tissues is promoted by means of a coil which is applied to produce a magnetic field at the site in which growth is to be encouraged. The coil is supplied with a low frequency alternating voltage below 50 Hz. A device is applied to the body or implanted in the body in order to concentrate the magnetic field produced by the coil.

United States Patent Kraus et al.

ELECTRICAL APPARATUS GENERATING A LOW FREQUENCY, ALTERNATING MAGNETICFIELD FOR PROMOTING THE GROWTH OF BONE AND OTHER BODY TISSUES lnventors:Werner Kraus, Munich; Hans-Dieter Viehbach, Aisingerwies, both ofGermany Assignee: Werner Kraus, Munich, Germany Filed: Apr. 6, 1972Appl. No.: 241,727

Foreign Application Priority Data Apr. 6, 1971 Germany 2116869 US. Cl128/15; 128/821; 128/419 F Int. Cl Afiln 1/42 Field of Search 128/1 R,1.3, 1.5, 82.1,

References Cited UNITED STATES PATENTS Brown 128/15 PrimaryExaminerWilliam E. Kamm Attorney, Agent, or F irm--Spencer & Kaye Thegrowth or repair of fractured bones or the growth of other body tissuesis promoted by means of a coil which is applied to produce a magneticfield at the site in which growth is to be encouraged. The coil issupplied with a low frequency alternating voltage below 50 Hz. A deviceis applied to the body or implanted in the body in order to concentratethe magnetic field produced by the coil.

ABSTRACT 5 Claims, 8 Drawing Figures PATENTED JUN 2 4 I975 SHEET I SHEETPATENTEDJUN'24' 1915 PATENTEDJUN 24 ms 3 SHEET Fig. 8

BACKGROUND OF INVENTION .1. Field to which Invention Relates Thepresent'invention relates to an apparatus for promoting the growth ofbone and other body tissues.

It is known that the shifting of an electrochemical equilibrium exisitngin a living organism can lead to a change in a mechanical state in theorganism. Proceeses of this type are continuely taking place in muscletissue. Furthermore the contraction and expansion of fibers of collagen,that is to say the connective tissue substance, has been observed totake place following a change in the concentration ofa salt solutionsurrounding the fibers.

One example of the reversability of this principle is offered by thepiezoelectric behavior of bone: In this case electrical deformationpotentials, which arise owing to mechanical loading of bone fiber,regulate the dynamic equilibrium between the free calcium and phosphateions in the blood, on the one hand, and the bound calcium and phosphateions in the crystal lattice of the hydroxyl apatite on the other.

The changes in state occurring are thus due to the disturbance of anexisting mechanical-chemical equilibrium between free and bound ions.The restoration of the original electro-neutrality is determined by thespeed of diffusion of the free ions and the statistical distribution inthe vicinity of the bound ions.

2. The Prior Art g k In accordance with aprevious proposal the reunionof fractured bones was to be encouraged by alternating electriccurrents, which were produced by means of a .pick-up coil which wasattached to a splint (induction splint) serving for holding the bone inplace. The splint had electrodes which extended into the gap of thefracture and the like. V

In the case of. clinical application of induction splints" of theproposed type effects were observed which cannot be completely explainedon the basis of the galvanic action of the induced currents. On thebasis of the above-mention ed considerations the idea then arose thatelectro-dynamical occurrences and such occurrences are involved in thecase of the abovedescribed mechanical-chemical changes in equilibriummust be accompaniedby corresponding magnetic fields and that it should.however, also be possible to produce corresponding chemical and physicalreactions by the action of electromagnetic fields in biological sy tems.Experiements carried out along these lines, which were aimed atdistinguishing the biological actions of the electric field and that ofthe magnetic field, proved this assumption to be correct. It was foundin this respect that the application at certain times and at certainlocations of electromagnetic fields led to growth of bone and other bodytissues. As a consequence of the action of the magnetic field aformation of new vessels occurringas a' primary factor was detected.

SUMMARY OF INVENTION On the basis of discoveries one aim of the presentinvention is to provide an electricalapparatus for proniotirigthe growthof bone and other body tissues.

The present invention resides in an electrical apparatus for promotingthe growth of bone and other body tissues comprising a generator for thesupply of low frequency alternating current with a frequency below 150Hz, a coil which can be connected with the output of the generator andwhose shape is adapted to the shape of the body part in which the growthof tissue is to be promoted and to the structure of the tissue to begrown,

and a device which can be applied to the body part for concentration ofthe field produced by the coil on to the zone of the body in which thetissue is to be grown. The device which can be applied to the body partcan if necessary be implanted in the body.

With the apparatus in accordance with the invention substantialsuccesses in healing have already been obtained in practice. For examplein the case of severe accident casualities involving fractures, the timefor repair of the fracture was reduced to half the normal time requiredfor healing. Furthermore, the healing of bed sores could be broughtabout or substantially accelerated.

LIST OF FIGURES OF DRAWINGS Further development of the invention aredefined in the subclaims.

In what follows embodiments of the invention will be described withreference to the accompanying drawings in detail.

FIG. 1 is a diagrammatic representation of a generator and a field coilof an apparatus in accordance with one embodiment of the invention.

FIGS. 2 and 3 show in perspective other types of field coils for adevice in accordance with the invention.

FIG. 4 is a sectional view of a fractured thigh bone with a marrow orKuntscher nail or pin, which comprises a field-concentrating device inaccordance with one embodiment of the invention.

FIG. 5 is a diagrammatic representation of an applied compression screw,which also comprises a fieldconcentrating device in accordance withtheinvention.

FIG. 6 shows a splint with embedded or inserted magnetic cores for thepurpose of field concentration.

FIG. 7 shows a device for field concentration which can be implanted.

FIG. 8 shows a Kiintscher nail or pin, which comprises a magnetic coreserving both for field concentration and also the inductive productionof a galvanic current in the bone region.

DESCRIPTION OF PREFERRED EMBODIMENTS The apparatus showndiagrammatically in FIG. 1 comprises a AC generator 10, which supplieslow frequency AC at the output terminals 12. The frequency of the AClies below 150 Hz, for instance between I and or Hz. It has been foundparticularly favorable to use a frequency range between 5 or 10 and 30Hz, for example 25 Hz. The half cycles of the alternating current shouldhave comparatively gently sloping leading and trailing flanks (rise andfall times of the half cycles being for example in the order ofmagnitude of a quarter to an eighth of the length of a cycle); the ACcan thus be a sinusoidal current with a low non-linear distortion, forexample less than 20 percent, or preferably less than 10 percent, or atriangular wave current.

The rise and decay times of the cycles can be in the order of onequarter to one eighth of the cycle.

It is also possible for the current to consist of sinusoidal ortriangular pulses with alternating polarity, which alternate eitherindividually or in pairs with pulse intervals. It is clearly importantin all cases that the front and trailing flanks of the current pulses orAC half cycles should slope relatively slightly. The rise and fall timesare preferably substantially greater than 5 ms (corresponding to asinusoidal current of 50 Hz), and preferably at least approximately 8 to10 ms, for example up to 80 ms.

On the AC signal it is possible to superimpose a DC component and/or anAC component with a higher frequency by means of a modulating devicecontained in the generator 10. The frequency of the component with thehigher frequency can amount, for example, to three to 10 times the basicfrequency of the AC signal. It is also possible for a DC component to besuperimposed on the AC signal so that the latter is asymmetric withrespect to the zero line.

The output terminals 12 of the generator 10 are connected with a fieldcoil 14, which in the case of the embodiment shown comprises aninsulated copper ribbon in the form of an U-shaped flat coil on aflexible flat ,core. The windings of the coil thus comprise tworespective bends of l80between which long relatively adjacently runninglongitudinal parts lie, which are bent in a U-shape. The particularshape of the coil is selected for producing a magnetic field B, whosedirection is adapted to the structure of the bone or other body tissuewhose growth is to be promoted. If, for example, an extremity 16, asindicated in broken lines, for example a thigh with a fractured femur isto be treated, the magnetic field B preferably runs in the direction inwhich the thigh bone is loaded during normal use, and

' the function of the blood vessels is encouraged.

Preferably, however, it is not only the spatial orientation of themagnetic field which is adapted to the circumstances present in theliving organism, but also the timing. In additon to'known spatialstructures of bone and other body tissues, the timing of the effect isalso of significance. The most important change with time of themechanical influences acting on the substance of the organism from theinside follows the heart beat.

The rhythm and form of the spread of the pressure wave of the blood inthe organism determine the metabolic events with their biochemical andbiophysical reactions to a substantial extent. For this reason actuationand/or control of the generator 10, and thus of the electromagneticfields produced, is provided for by the systolic pressure wave in thezone of application. This can be carried out in particular with a pulsepressure wave detector 18, which is applied adjacent to the treatmentzone between the latter and the heart on the body part to be teated.

The actuating pulse produced at the pulse detecting device 18 inaccordance with the systolic pressure wave can be used in a generator 10for initiating an individ- ,en line loops.

the function corresponding to the systolic pulse pressure wave ofahealthy person with blood vessels which are still elastic, moreparticularly a young person.

FIG. 2 shows another embodiment of a field coil which can be used forthe present device. The field coil in accordance with FIG. 2 consists ofa number of flat coils 14a, the shape of whose windings is indicated inthe case of the uppermost coil by solid lines 20. The flat coils 14a cancomprise ferromagnetic laminations and are connected at the sidescorresponding to bends in the windings in a hinged manner so that thefield coil 14', consisting of the flat coils connected in parallel or inseries, can be applied as desired about a body part in order to inducein the latter a magnetic field, whose direction is indicated by thedouble arrow B, the paths of fields of the individual coils beingindicated by brok- The flat coils 14a can on the other hand be connectedat the end faces 15 in a hinging manner with each other, if the fieldcoil is required for treating the spinal column for example.

The field coil 14" in accordance with FIG. 3 corresponds in principlewith the field coil in accordance with FIG. 2 with the exception thatthe coils 14b, which are connected together in a hinged manner, have acircular cross-section.

Instead of flat coils 14a or coils 1417 with a circular cross-section itis naturally also possible to use other suitable coil forms, for examplecoils with an elliptical cross-section. I

As a coil a cylindrical or solenoid coil 40" is to be used, as indicatedin FIG. 4.

If desired the distribution of windings on the field coils can be unevenin order to obtain a field concentration. For example the windingdensity in the case of the coils l4, and 14" can increase from theoutside in an inward direction or it is possible to connect additionalnarrower coils which can be slid on in order to achieve the desiredfield distribution.

The solenoid coil 14" in F IG; 4 has such a large internal diameter thatit can he slid over an extremity to be treated, for example a thigh 22,for example when the healing of the fractured femur 24 is to bepromoted. The bone 24 is pinned in a conventional manner with aKiintscher nail 26 or pin, in whose interior a field concentratingdevice of a rod-shaped body 28 of ferromagnetic material with a highinitial magnetic permeability and a low remanence is used, that is tosay a magnetically soft" material. The body 28 is fixed by staples 30 inthe desired position. It brings about a concentration of the magneticfield at the site of the fracture 32. The core is coated with an inertpolytetrafluoroethylene layer. In a manner similar to the arrangement tobe described with reference to FIG. 7, it is also possible to provideseveral cores with a spacing between them in the nail or pin and betweenthe cores a relatively strong leak field occurs which promotes growth.This leak field extends into the gap in the fracture or the site of thefracture.

FIG. 5 shows a so-called compression screw 34, which is provided with anaxial hole, in which a ferromagnetic body 36, serving for fieldconcentration, is located. which preferably is also made of amagnetically soft material.

FIG. 6 shows a splint which 'canbe implanted or support plate as isconventional in principle for fixing fractured bones, with which it isconnected by screw means. In the construction shown in FIG. 6 there is,however, the novel feature that it comprises embedded or inserted bodies40 of ferromagnetic material in order to bring about a concentration ofthe magnetic field produced by the field coil adjacent to the fracturedbone.

Since with the invention a comparatively rapid restoration of the boneand other body tissue can be achieved it is possible to make the splint38 and other corresponding support structures (pins etc.) so as to besubstantially lighter than has been the case to date. For example thesplint 38 can be made of plastics material and can be used only forfixing the bone fracture parts, since the bone will be rapidly repairedto such an extent that it can carry the load itself.

Preferably such support structures are made of organic material, forexample cut or milled from animal bone. This material, which must befreed of protein, may then possibly be absorbed by the living body, canthen possibly be absorbed or taken up by the body, so that subsequenttreatment is substantially simplified. The production of bone fracturesupport parts such as pins or nails, plates, half-shells and screws ofbone substance or synthetically produced molded parts, which are treatedwith calcium and orthophosphates and can be taken up by the body, offersadvantages not only with the present purpose.

FIG. 7 shows a further apparatus for producing a field concentration. Itcomprises a flexible tube 42 of an inert material such as polyethylene,in which rodshaped bodies 44 of a metnetically soft material with a highpermeability are embedded. The flexible tube 42 can be shrunk after theinsertion of the bodies in order to fix the bodies 44 with a spacingbetween them. The flexible tube with the bodies 44 can then be embeddedin the tissue to be renegerated.

The position of the magnetic core 44, see FIG. 7, in the flexible tube42 can also be fixed by means of distance pieces 43, such as pieces ofpolytetrafluoroethylene, which are arranged between the cores.

The marrow or Kiintscher nail 26' or pin shown in FIG. 8 comprises, asis the case with the nail 26 in accordance with FIG. 4, a magnetic core28', which serves for field concentration at the site of fracture.Furthermore the core carries at least one winding 46, in which the lowfrequency magnetic field produces an alternating voltage. The ends ofthe winding are connected with bare platinum-iridium electrodes 48,which may be in the form of wires or metal sheet. The electrodes arearranged on an insulated section 50 of the outside of the nail or theycan be embedded in an insulated manner in the outside of the nail. Thealternating current flowing between the electrodes 48 through thefracture site also encourages the healing process and callus formation,as has already been proposed in connection with the splint.

Instead of using magnetically soft material, it is also possible to usea ferromagnetic material with a relatively low remanence, which is soselected that a certain premagnetisation can be set and thispremagnetisation has superimposed on it the alternating magnetisation asproduced by the field coil. The same effect can be achieved bysuperimposing a DC component on the AC supply to the field coil.

It is naturally possible for other coil and magnetic core arrangementsto be used in order to concentrate the low frequency alternatingmagnetic field adjacent to the organism, in which the growth orregeneration of tissue is to be promoted. The direction of the magneticfield lines then preferably runs parallel to that of the fiber or vesselstructure.

All parts coming into contact with the body substance consist of aphysiologically compatible material, at least on their surface.

What is claimed is:

1. In an electrical apparatus for promoting the growth of bone and otherbody tissues by the application thereto of a low frequency alternatingmagnetic field, such apparatus having current generating means and fieldapplicator means, the improvement wherein the applicator means comprisesa flat solenoid coil having an axis about which the coil is wound andcomposed of a plurality of parallel and flexible windings, each saidwinding having two adjacent elongate portions and two coil bends joiningsaid elongate por tions together, said coil being flexible in the coilplane in the region of said elongate portion for being bent into aU-shape, said coil being bent into such U-shape about an axis parallelto the coil axis and adapted for connection to a source of low frequencyalternating current.

2. In an electrical apparatus for promoting the growth of bone and otherbody tissues by the application thereto of a low frequency alternatingmagnetic field, such apparatus having current generating means and fieldapplicator means, the improvement wherein the applicator means comprisesa U-shaped flat solenoid coil having an axis about which the coil iswound and composed of a plurality of parallel windings, each saidwinding having two adjacent, elongate U-shaped portions and two 180 coilbends joining the ends of said elongate portions together, the coilbeing curved in such U-shape about an axis parallel to the coil axis andadapted for connection to a source of low frequency alternating current.

3. In an electrical apparatus for promoting the growth of bone and otherbody tissues by the application thereto of a low frequency alternatingmagnetic field, such apparatus having current generating means and fieldapplicator means, the improvement wherein the applicator meanscomprises: a plurality of solenoid coils each having an axis about whichsuch coil is wound and disposed adjacent one another with their axesparallel and adapated for connection to a source of low frequencyalternating current, and hinge means connecting adjacent coils togetherfor pivotal movement about axes parallel to the axes of said coils.

4. An arrangement as defined in claim 3 wherein said coils having acylindrical cross section.

5. An arrangement as defined in claim 3 wherein said coils have anelliptical cross section.

* l l l

1. In an electrical apparatus for promoting the growth of bone and otherbody tissues by the application thereto of a low frequency alternatingmagnetic field, such apparatus having current generating means and fieldapplicator means, the improvement wherein the applicator means comprisesa flat solenoid coil having an axis about which the coil is wound andcomposed of a plurality of parallel and flexible windings, each saidwinding having two adjacent elongate portions and two 180* coil bendsjoining said elongate portions together, said coil being flexible in thecoil plane in the region of said elongate portion for being bent into aU-shape, said coil being bent into such U-shape about an axis parallelto the coil axis and adapted for connection to a source of low frequencyalternating current.
 2. In an electrical apparatus for promoting thegrowth of bone and other body tissues by the application thereto of alow frequency alternating magnetic field, such apparatus having currentgenerating means and field applicator means, the improvement wherein theapplicator means comprises a U-shaped flat solenoid coil having an axisabout which the coil is wound and composed of a plurality of parallelwindings, each said winding having two adjacent, elongate U-shapedportions and two 180* coil bends joining the ends of said elongateportions together, the coil being curved in such U-shape about an axisparallel to the coil axis and adapted for connection to a source of lowfrequency alternating current.
 3. In an electrical apparatus forpromoting the growth of bone and other body tissues by the applicationthereto of a low frequency alternating magnetic field, such apparatushaving current generating means and field applicator means, theimprovement wherein the applicator means comprises: a plurality ofsolenoid coils each having an axis about which such coil is wound anddisposed adjacent one another with their axes parallel and adapated forconnection to a source of low frequency alternating current, and hingemeans connecting adjacent coils together for pivotal movement about axesparallel to the axes of said coils.
 4. An arrangement as defined inclaim 3 wherein said coils having a cylindrical cross section.
 5. Anarrangement as defined in claim 3 wherein said coils have an ellipticalcross section.